Abstract
Mechanistic proposals for the C-H activation reaction enabled by mono-N-protected amino acid ligands (MPAAs) have been supported by DFT calculations. The direct experimental observation of the ligand-assisted C-H activation has not yet been reported due to the lack of well-defined isolated palladium complexes with MPAAs that can serve as models. In this work, palladium complexes bearing chelating MPAAs (NBu(4))[Pd(κ(2)-N,O-AcN-CHR-COO)(C(6)F(5))py] (Ac = MeC(O); R = H, Me) and [Pd(κ(2)-N,O-MeNH-CH(2)-COO)(C(6)F(5))py] have been isolated and characterized. Their evolution in a solution containing toluene leads to the C-H activation of the arene and the formation of the C(6)F(5)-C(6)H(4)Me coupling products. This process takes place only for the ligands with an acyl protecting group, showing the cooperating role of this group in a complex with a chelating MPAA, therefore experimentally validating this working model. The carboxylate group is inefficient in this C-H activation.